The use of slow release bolus formulations which provide animals with small daily dosages of materials over extended periods of time has been shown to be an effective alternative to repeated treatments.
While considerable research has been undertaken to provide novel bolus compositions utilizing various materials to obtain the desired release rates, such as those described in British Patent Application No. GB 2077103A and U.S. Pat. No. 4,444,927, which employ biodegradable polymers and polydioxanones, respectively, relatively little research has been reported on specific manufacturing processes suitable for their preparation or the effect of the process used on the performance of the bolus.
U.S. Pat. No. 4,166,107 describes effective, sustained-release bolus formulations, containing insect growth regulators with a mixture of a wax, a fat and barium sulfate, useful for the control of arthropods in manure, that are prepared by atmospheric molding or by compression molding.
It is an object of this invention to provide an injection-molding method for the preparation of sustained release bolus formulations containing insect growth regulators or other veterinary compositions, which is suitable for the manufacture of commercial quantities of sustained release boluses.
It is another object of this invention to provide improved, uniform performance of sustained release bolus formulations by utilizing the method of the invention.